Process for the hydrogenation of coal



NOV- 10, 1953 E. F. PEVERE Er A1.

PROCESS FOR THE HYDROGENATION OF COAL Filed Nov. 19, 194e Patented Nov.10, 1953 UNI-TE D STATES offre-free;

PR OCES SfFOR lRO'GETN`- Ernest Ft Pevereand Howard V. Hess, Beacon,

and' George? B; Arnold,.Glenhan1,-z N; Y., lassignors toThe TexasCompany,Newllorkyllflila` a; corpora'tioxrofl Delawarev Application.'November 19, 1918"; Serial l`-'No.=- 61,012T

This invention relatesto,aprcee'ssl for the hydrogenation of co'a1.' Theprocess ofthisinvention is particularly applicable to the treatment ofbituminous coals. r.

In the conventional coal-'hydrogenation processes, suchoas practicedinG'ermanythe coal is dried, pulverized, and made intooa paste.v Heaviroil derived from the process is admixedlwith the powdered coal inapproximately equalproportions by Weight to formthe'paste.Ahydrogenation catalyst, e. g., iron sulfate' in an amount equivalent toaboutV 1 per cent by Weight,.is incorporated'in thejpaste.' The paste ismixed with hydrogen, preheated to. the operating temperatures, generallyabout 850`F.', and' passed into convertersunder a pressure of fromabout4,0'00 to about` 10,000 pounds per square inch. Thisst'ep is calledthev liquid'phasehydrogenation stepof the process; Vapo'rs arekseparated" from. there'- sidual solids and liquid'A at the operatingpressure and temperature. nreact'ed hydrogen and most of the oil areremoved as vapors; Thetvapors are cooledtocondense theoil, andV and thehydrogen isrecycled. Heavy" oil is separated from' theresidualI solids.The heavy oil' is' used for preparing thepaste, while residua-l solidsare used' asfuel'. The light oils are subjected to' vaporphasehydrogenationfor conversion'togasoline. In this step, oil vaporsandhydrogen are passed: over a=cata1ys't,.e;.g.., tungsten sulfide, at apressurey of about`4,500 pounds perf square inch: Oils` boiling abovethe"V motorv fuelY boiling'v range arerecycledto the process;

An important element of cost in conventional coal liquefactionVprocesses is in the preparation ofl the coal` for hydrogena'tion". Inthe process of the present invention it. is not necessary tofpul- Verizethecoal'feed or to'prepare a paste in conventional manner. Eliminationof the pulveriz'- ing and conventional pasting steps resultsin asubstantial` saving in operating costs;

A11-object of this-inventionfisI toiprovde animproved process for thehydrogenationfof coal.

Another Objectis to provide animproved'process for the production of oilfrom coa-lby-liquid phase reaction of coal with hydrogen;

Other objects and advantageswill be apparent to those skilled in theartfrom the following detailed descriptionv of the invention;

In accordancel with the' process! of this'l inven'- tion, coal isliquefied, theli'uueed coal isatuI-i'ill` ized, and subjected tohydrogenation' in a dls" persed condition' at anA elevated temperature:andi pressure, Y

Coal may be rendered plasticby heating; The

plastic point varies with different lcoals. Gren'L erallyV -coal'lbecomes plastic.y or: liqueiiesat f a temperature-Withinthe range` of`fromifabout. '550 to about- 7 00 'F'. When coall is. heated-"in" the.Ipresience of a: mineral-oil, the? coaland. oil` become miscible and: maybe mixed: to-form'. aI substanitially homogeneousl `viscous'sliquid.Somerhydroy carbon oils;` Vespecially hydroaromatics; suoli as tetralin,decalin, and heavy oils obtained by hydrogenation: ofcoal,v actas:solventsA arid aid'V in the. liquefaction the coal; At" temperaturesabove about 700 F., there'isa' condensationr of free radicals? or.unsaturated: compounds (generiated by thermal-decomposition of coalsubstance) into materialsV more 'stab-le; than theoriginallcoalsubstances. At temperatures above* about? 825 E., the ratecfvprecipitatio-nof insolublepolymer may exceedthefrate cffi'liquefaetion;Thecoal should be kept at: av temperature: as;y lowaspos'- sibledur-ing;liquefaction. andisubsequent': handlingfintheliquidistate?tc'preventexcessive precipitation'- off the' solid:polymer; The optimum temperature.. for liquefactionf isf dependent Yupon the. type and source# off. the: coal an'dthe"v length off time/'inwhichthefcoali niust bekeptin lliquid state' prior to hydrogenation'andi isi best` determined by trial-for anygiven coal;

When tlfxeiA coal.- isiliquefied'witli the oil with mechanical mixing.;d aA substantially homogeneous liquidf'mixturermay bei' obtained; Finelydivided solid particles may lierpresent. in` the mixture. This mixturemay beatomizedswtliout further treatment. Oni the otherhand"1 when' thepar'-r ticles-ofv coal are extractedI Withr oil'without agi--tation.abouty 65v` per; cent biyweight'of the coal is-ftak"en:.intosolution. .in the oiI leaving' a1 porous riabler residue; The liquefied.coal or' extract ob-v tained'. '.by` this'v method iis substantiallyfree' from ash: The undissolve'cl portioniofthecoalissuitable forreaction,.inrsituftoiproduce carbon mon-y oxideA and l.hydrogexr by.reactiomwitli steamV or with-fa; mixture of steamkandoxygen; Witheith'ermethodo liquefaetionthe residual solids :may be used forthefgeneratiorrof syntiiesis-ga'sesorfor' production. of: hydrogen. forthe process InA accordancefwth:preferred: practice of` this invention;ccal= and o'I are` admixed toform a'- liduiaatatemperatureWithin@therangerof about 550 to 850 F. and the resultingli'quiisatomized." intol at hydrogenatiort-'reaotor' operated-fat atemperature-zwithin. the range off from about '750 to about 850 F. and apressureA aboveabout 1000. pounds. per suda-ref inch-1 gauge. Hydrogenis=.pref'erab1y-usecias adi'spersing rrieui'uiii for" atomzation ofthercoal r"llieividalmay lbe liql-f fed at a temperature of 550 to '700F. and the resulting liquid heated to a temperature within the range offrom about 750 to about 850 F. prior to hydrogenation.

The quantity of liquid admixed with the coal to form a liquid streamwhich may be atomized with conventional equipment may vary considerablydepending upon the type of coal and oil' used in the preparation step.Generally, a quantity of oil equivalent to about 50 per cent by Weightbased on the weight of the coal is sufficient to provide a fluid feedstream which may be atomized.

The particle size of the coal fed to the process is not of particularimportance. The smaller particles are more quickly liquefied. 'Iheparticles should be of such size that substantially completeliquefaction takes place in a reasonable period of time. Generally it isdesirable to use particles ranging from about x/z-inch in averagediameter to powder.

With the present process it is not necessary to resort to fine grindingor pulverization of the coal prior to preparation of the feed as inconventional hydrogenation processes. It is contemplated that in mostapplications of the process, the coal will be reduced only to a particlesize such that the largest particles are dissolved prior to discharge ofthe liquid from the liquefaction vessel. Coal may be crushedmechanically to a particle size of 1/g-inch to 1/il-inch in averagediameter with a relatively small expenditure of power. Further reductionin size becomes progressively more expensive, pulverization byrnechanical means requiring large expenditures of power. The process ofthe present invention represents a considerable saving in powerrequirements for the preparation of the feed over conventional methodsof preparation.

The atomized coal maybe hydrogenated under conditions satisfactory forconventional liquid phase hydrogenation of coal. Liquid phase coalhydrogenation is a well-known procedure. In atomized form, the liqueedcoal is more reactive than in conventional paste form, hence the timerequired to effect a given percentage of conversion is somewhat lessthan for conventional procedures. The pressure under which the coal ishydrogenated may range from 1,000 to 10,000 pounds per square inch gaugeor higher, and the temperature from 600 to 900 F.

In a preferred embodiment, the liquefied coal is atomized and suspendedin hydrogen. rIhe suspension is introduced into a uidized bed ofresidual solid material resulting from the coal hydrogenation reaction.The solid residual particles are entrained in the product stream and areseparated from the oil in subsequent separation steps of conventionaldesign. The residual solid material contains unreacted carbon as well asash from the coal and may be used as fuel or reacted with steam or withsteam and oxygen to produce a mixture of carbon monoxide and hydrogen.About '70 per cent by weight of the coal charged to the process may beconverted to Iiuid products by hydrogenation, the hydrogen consumptiongenerally ranging from about 1.5 to about 3 per cent by weight based onthe Weight of the dry coal.

The invention will be more readily understood from the followingdetailed description and the accompanying drawing.

The gure is a diagrammatic elevational view illustrating a preferredinode of carrying out the process of the present invention.

With reference to the drawing, coal of a suitable particle size issupplied to a hopper 5 through a conduit 6. From the hopper the coal maybe fed through conduit 'I into liquefaction vessel 8 or through conduit9 into liquefaction vessel I0. Any number of such vessels may beemployed. With two vessels, as illustratedone of the vessels is chargedwith coal and cil to prepare a liquefied coal feed stream forhydrogenation While the other is being discharged to the hydrogenationreactor. When a vessel has been filled with coal from the hopper, inertgas from line I2 may be admitted to the vessel to purge it of air. ValveI3, associated with vessel 8, and valve I4, associated with vessel I0,are provided for this purpose. Air and other gases may be vented fromthe vessels to line I5. Gases from vessel 8 are vented to line I5through valve I6; those from vessel I0, through valve II.

Preheated oil from line IB may be admitted to vessel 8 through valve I9and to vessel I0 through valve 2G. When a vessel is lled with coal andoil the valves are closed and the coal particles at least partiallyliqueed due to the combined effect of heating and the solvent orplasticizing action of the hot oil. A substantially homogeneous liquidmixture of coal substance and oil is thus obtained.

Mechanical mixers, not illustrated in the drawing, may be supplied toinsure complete disintegration of the coal, if desired.

As illustrated in the drawing; the coal is subjected to intimate contactwith hot oil without agitation, effecting solution of a part of the coalin the oil and leaving a porous friable residue in the liquefactionvessels 8 and I0. The resulting liquid, comprising liquefied coal andoil, is discharged from vessel 8 through valve 23 and from vessel I0through valve 24 to a charge pump 25 as feed for the hydrogenationstep..

Inert gas from line I2 may be admitted to the vessel during the periodof discharge to the feed pump. Gas from line I2 may be supplied underpressure to build up a pressure Within the vessel and aid in the removalof liquid from the residual solid. This gas may be heated if desired toan elevated temperature. This porous friable residue remaining in theliquefaction vessel is in a state nearly ideal for gasification, Amixture of steam and oxygen may be supplied to the liquefaction ofvessels through line 21. The ow of gas from line 21 is controlled byvalves 28 and 29, associated with vessels 8 and I0, respectively. Theresulting products of gasification may be discharged into line I5 forfurther use as desired.

Catalyst may be admitted through line 30 into admixture with the streamof liquefied coal and oil.

From the charge pump 25 the liqueed coal and oil stream is passedthrough a heating coil 32 and charged through line 33 into an atomizer34 associated' with a hydrcgenation reactor 35. The coal feed stream maybe fed directly from the charge pump 25 to the atomizer 34 through line36 as controlled by valve 37. Since it is generally desirable to carryout the hydrogenation reaction at a pressure above about 1,000 poundsper square inch gauge and often not desirable to subject the heatingcoil 32 to excessive pressure, a second charge pump 38 may optionally beprovided to increase the pressure of the hot charge stream immediatelyprior to introduction of the stream to the atomizer 34.

Hydrogen is admitted to the system through line 49. Fresh and recycledhydrogen are pumped by a pump 4l through line 42 into the atomizer 34.In the atomizer 34, which may be of any conventional type, the liquefiedcoal feed stream is broken up into small droplets and dispersed in thestream of hydrogen from line 42. From the atomizer, the dispersion ofliquefied coal and hydrogen is discharged directly into thehydrogenation zone 35. In the dispersed state, the hydrogenationreaction proceeds rather rapidly.

Somewhat more hydrogen is usually required for atomization anddispersion of the atomized coal stream than is required in theconventional liquid phase hydrogenation. This merely results in a higherrecycle rate, since hydrogen consumption, for a given percentageconversion, is not appreciably affected.

The hydrogenation reaction results in precipitation of ash and the moredifcultly hydrogenatable fraction of the coal substance as solids. Thesesolids are entrained in the eilluent stream discharged from thehydrogenation zone 35 through line 4l'. The hydrogenation eiliuent ispassed to a separation system 48 wherein it is separated into variousfractions. Any of several known conventional methods of separation maybe employed. A gaseous fraction is recycled to the hydrogenation reactorthrough line 4Q to pump 4 I. A portion of the gaseous fraction may bepurged from the system through line 5|. A light oil fraction is takenfrom the separation system through line 52 and a middle oil fractionthrough line 53 for further processing. In accordance with generalconventional practice, the middle oil stream is subjected to furtherhydrogenation in vapor phase to produce motor fuels. Residual solidsseparated from the oils in the separation system 49 are dischargedthrough line 54.

Heavy oil is discharged from the separation system through line 56 as arecycle stream to the liquefaction vesels 8 and I0. A portion of theheavy oil may be withdrawn for other uses through line 57. Other oilsmay be supplied if desired to the heavy oil recycle stream through line58. The heavy oil stream is heated in a heating coil 50 to the desiredtemperature prior to `admission to the liquefaction vessels 6 and I0through line i8. All of the heat required for the process may besupplied by the hot oil stream.

It will be understood by those skilled in the art that variousalternatives are available in the way of equipment and methods ofhandling the various streams and utilizing the heat contents to maximumadvantage. In the interest of simplicity, various conventional pieces ofapparatus such as control valves, heat exchangers, and the like, havebeen omitted.

In a typical operation of la process such as illustrated in the drawing,Pittsburgh Bed coal containing about 2 per cent water, 31 percentvolatile matter, 58 per cent fixed carbon, and 9 per cent ash, asreceived, is subjected to hydrogenation. The coal is charged to aliquefaction vessel in the form of lumps about 1/2 to 1A inch in averagediameter. This coal is mixed with heavy oil obtained from thehydrogenation of coal in an amount approximately equal in weight to theweight of the coal. The oil is preheated to a temperature of about 850F. before admixture with the coal, resulting in a temperature of about750 F. in the liquefaction vessel. About 6 65 per cent by Weight of thecoal is liquefied or extracted by the liquid oil without agitation,leaving a rporous friable carbonaceous residue.

The resulting liquid comprising liquefied coal is atomized with hydrogeninto a reactor at about 750 F. and about 1,000 pounds per square inchgauge.

Obviously many modifications and variations of the invention ashereinabove set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A process for the hydrogenation of fusible coal which comprisescontacting particles of said coal having an average diameter smallerthan about l inch with a hydroaromatic oil at a temperature Within therange of from about 550 to about 850 F. and above the plastic point ofsaid coal, mixing the coal and oil at said temperature for a period oftime sumcient to form a substantially homogeneous liquid mixture,contacting said liquid mixture with hydrogen in a hydrogenation zone ata temperature within the range of from about 600 to about 900 F'. and apressure within the range of from about 1,000 to about 10,000 pounds persquare inch gauge whereby hydrogenation of said liquid takes place Withthe formation of particulate solid residue, maintaining a fluidized bedof said particulate solid residue Within said hydrogenation zone,discharging resulting Huid products of hydrogenation and solid residuefrom said hydrogenation zone, and recovering said fluid products.

2. A process for the hydrogenation of fusible coal which comprisescontacting particles oi said coal having an average diameter within therange of from about 1/4 inch to about 1/2 inch with a hydroaromatic oilat a temperature within the range of from about 550 to about 350 F. andabove the plastic point of said coal, mixing the coal and oil at saidtemperature for a period of time sucient to form a homogeneous liquidmixture, atomizing said liquid mixture, suspending the atomized liquidin hydrogen at a ternpertaure within the range of from about 600 toabout 900 F. and a pressure within the range of from about 1,000 toabout 10,000 pounds per square inch gauge whereby hydrogenation of saidliquid takes place with the formation of particulate solid residue,introducing said suspension at said hydrogenation temperature andpressure into a uidized bed of particulate residual solid materialresulting from the hydrogenation reaction, discharging the resultingfluid products of hydrogenation and solid residue from saidhydrogenation zone, and recovering said fluid products.

ERNEST F. PEVERE. HOWARD V. HESS. GEORGE B. ARNOLD.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,864,496 Pier et al June 2l, 1932 1,390,435 v Krauch et alDec. 6, 1932 2,215,190 Pier et al Sept. 17, 1940 2,436,938 Scharmann etal. Mar. 2, 1948 2,464,271 Storch etal Mar. 15, 1949 2,476,999 OrchinJuly 26, 1949

1. A PROCESS FOR THE HYDROGENATION OF FUSIBLE COAL WHICH COMPRISESCONTACTING PARTICLES OF SAID COAL HAVING AN AVERAGE DIAMETER SMALLERTHAN ABOUT 1/2 INCH WITH A HYDROAROMATIC OIL AT A TEMPPERATURE WITHINTHE RANGE OF FROM ABOUT 550 TO ABOUT 850* F. AND ABOVE THE PLASTIC POINTOF SAID COAL, MIXING THE COAL AND OIL AT SAID TEMPERATURE FOR A PERIODOF TIME SUFFICIENT TO FORM A SUBSTAN TIALLY HOMOGENEOUS LIQUID MIXTURE,CONTACTING SAID LIQUID MIXTURE WITH HYDROGEN IN A HYDROGENATION ZONE ATA TEMPERATURE WHITHIN THE RANGE OF FROM ABOUT 600 TO ABOUT 900* F. AND APRESSURE WITHIN THE RANGE OF FROM ABOUT 1,000 TO ABOUT 10,000 POUNDS PERSQUARE INCH GAUGE WHEREBY HYDROGENATION OF SAID LIQUID TAKES PLACE WITHTHE FORMATION OF PARTICULATED SOLID RESIDUE, MAINTAIN-